Method and apparatus for underwater drilling



1962 H. STRATTON 3,015,360

METHOD AND APPARATUS FOR UNDERWATER DRILLING Filed Aug. 19, 1957 3 Sheets-Sheet 1 2 /9 FIG.

ZNVENTOR. HAL S TRATTON A T TORNEYS Jan. 2, 1962 H. STRATTON 3,015,360

METHOD AND APPARATUS FOR UNDERWATER DRILLING Filed Aug. 19, 1957 3 Sheets-Sheet 2 F IG. 2

/I n i V I 64 V 68 INVENTOR. mug HAL .STRATTON METHOD AND APPARATUS FOR UNDERWATER DRILLING Filed Aug. 19, 1957 H. STRATTON Jan. 2, 1962 3 Sheets-Sheet 3 FIG. 3

HAL

INVENTOR.

.STRATTON A T TORNEYS United States Patent 3,015,360 METHOD AND APPARATUS FOR UNDERWATER DRILLING Hal Stratton, Pasadena, Calif., assignor to Shell Oil Company and Continental Oil Company, both corporations of Delaware, and The Superior Oil Company and Union Oil Company of California, both corporations of California, all of Los Angeles, Calif.

Filed Aug. 19, 1957, Ser. No. 678,902 8 Claims. (Cl. 166-46) This invention relates to apparatus and methods for drilling wells in underwater formations from a floating vessel.

Although the invention is applicable to drilling wells in formations under any body of water, it is described as applied to drilling wells in ocean beds. As the search for oil and gas, as Well as other minerals, moves farther offshore, the problem of drilling wells in relatively deep water increases.

At the present time, it appears that drilling from floating vessels offers the most economical method for drilling wells in relatively deep water, say in excess of 75 feet. However, one of the problems in drilling from a floating vessel is that of moving equipment to and from the well, particularly when the Well is being started. The wind, wave, and current action, which is almost invariably present, causes an anchored floating vessel to move within a limited orbit over the well site, sometimes making it difficult, for example, to re-enter a partially drilled well with a drill string. This invention provides apparatus and methods for starting a well in an underwater formation from a floating vessel and minimizing the dilficnlty of moving the equipment in and out of the well.

Ordinarily, after the initial portion of a well is drilled, it is necessary to cement a casing in the upper end of the well to provide support for the well and to permit drilling with return circulation. In the past, casing has been guided into the well over the drill pipe which is maintained in the well. This procedure works, but it requires alternately supporting the drill string from the floating vessel from two diiferent points While working sections of easing of limited length onto the drill pipe. With this invention, the drill pipe may be removed so that relatively long sections of easing are quickly and easily lowered into the well.

In terms of method, the invention contemplates drilling a well in an underwater formation from a floating vessel by anchoring the vessel over the formation, and disposing a guide conduit so that its upper end terminates at the vessel and its lower end terminates at the formation. Drilling equipment is moved between the floating vessel and formation through the guide conduit to drill a well. After the well is at least partially drilled, the drilling equipment is withdrawn from the well and guide conduit, and a casing is lowered through the guide conduit into the well.

In the presently preferred method, the casing is made buoyant enough to be self-supporting, so that the guide conduit can be removed by simply lifting it up from around the casing. Since the casing is self-supporting, the guide conduit is easily stripped up the floating casing and stored on the vessel. Also in the preferred meth- 0d, the lower end of the guide conduit is anchored to the formation to provide positive alignment of the guide conduit with the well, and the lower end of the guide conduit is held in a position spaced above the formation so that cuttings formed as the well is initially drilled can pass out of the upper end of the well, underneath the guide conduit, and on to the ocean floor.

In terms of apparatus, the invention contemplates a vessel floating in a body of water, means for anchoring Patented Jan. 2, 1962 the vessel over a well site, and a guide conduit depending from the vessel and terminating at the underwater formation. Means are provided for anchoring the lower end of the guide conduit in a fixed relation with respect to the formation, and means are also provided for holding the lower end of the guide conduit spaced above the formation. Means are also provided for drilling a well in the formation through the guide conduit.

In the preferred form, the guide conduit includes a slip joint so that with its upper end secured to the floating vessel, the conduit slides up and down as the vessel is moved by wave action. Also, the apparatus includes a casing adapted to slide down inside the guide conduit and into the well, and means are provided for capping the casing at its upper end so that it can hold a fluid lighter than water and be self-buoyant.

These and other aspects of the invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary schematic elevation showing a well being drilled from a floating Vessel in accordance with the invention;

FIG. 2 is a fragmentary schematic elevation of a casing being lowered into the well through the guide conduit; and

FIG. 3 is a fragmentary schematic elevation of the casing cemented in the well and mounted with its upper end to provide for drilling with return circulation.

Referring to FIG. 1, a floating vessel 10, such as a ship or barge, is anchored by anchor lines 11 in a body of water 12 over an underwater formation 13 in which a well is to be drilled. A draw works 15 and a power unit 16, which may be of conventional type, are mounted on the vessel to operate a hoisting cable 17 carried over a crown block 18 located at the upper end of a derrick 19 erected on the deck of the vessel.

The traveling end of the hoisting cable carries a traveling block 20 and a hook 21 which supports a swivel joint 22. A kelly joint 23 extends downwardly from the swivel through a kelly bushing 24 in the center of a rotary table 25 mounted on gimbals (not shown) in a manner such as described in US. Reissue Patent No. 24,083. The rotary table is supported by a platform 26 directly over a cellar or opening 27 which may be located in the center of the vessel. Power is supplied to the rotary table through a shaft 28 turned by a rotary table power unit 29.

The upper end of a downwardly extending and tubular guide conduit 32 is supported by tie rods 33 in the center of the cellar above the water level. The guide conduit includes an upper section 35 which has a slip joint 36 at its lower end fitting in the upper end of a lower section 38 of the guide conduit. Stops 40' on the mating ends of the guide conduit sections prevent the inadvertent separation of the guide conduit. An annular buoyant chamber 42 welded around the upper end of thelower section of the guide conduit maintains the guide conduit in an upright position. An annular anchoring base 44 is secured around the lower end of the guide conduit and has downwardly extending spikes 46 which penetrate the formation to holdthe lower end of the guide conduit in alignment with the well and to space the lower end of the guide conduit BbOVCfllS ocean floor. The length of the guide'conduit gives. it sufiicient flexibility to accommodate the limited movement of the vessel. In water of such shallow depth that the guide conduit might be damaged due to lateral movement of the vessel, v

a flexible joint (not shown) is included in the guide con- 3 duit into the well. Drill collars 50 and a drill bit 52 are attached to the lower end of the drill string.

A mud hose 54 is connected atone end to the swivel and at theother end to a pump 55 so that a drilling fluid can be circulated down the kelly joint, drill pipe, and out the lower end of the drill bit' as the well is drilled.

The operation of the apparatus is as follows: After the vessel is anchored over the well site, the guide conduit is lowered until the spikes penetrate the formation and secure the lower end of the conduit in a fixed position with respect to the ocean floor. The buoyant chamber on the guide conduit maintains it in an upright position, and the tie rods keep the upper end of the guide conduit centered in the cellar of the vessel. The drill bit is lowered to contact the formation, and a drilling fluid, usually salt water, is circulated out the lower end of the bit as it is rotated by the rotary table. As cuttings are formed, they are carried by the drilling fluid up the annular space between the drill string and the well bore, and are deposited on the ocean floor underneath the lower end of the guide conduit. No attempt is made to drill with return circulation at this time. If it is necessary to remove the drill string from the well, say to change drill bits, the guide conduit provides a positive guide for the equipment being moved between the floating vessel and the well.

After the well has been drilled to a depth which depends on the type of formation encountered, it is usually desirable or necessary to set a casing to support the walls of the well and provide for drilling with return circulation for control of the well in the event high pressure formations are encountered. Apparatus for this phase of the drilling operation is shown in FIGS. 2 and 3.

.Referring to FIG. 2, the drill string is withdrawn from the well and guide conduit, and the rotary table is removed from the platform. A casing 60 made up of welded individual pipe sections is assembled and lowered by the hoisting cable down through the guide conduit and into the well. Since there is no drill string in the Well, the casing can be quickly made up into relatively long lengths and lowered into the well without having to strip the casing down over a string of drill pipe supported from the floating vessel. After a suitable length of casing is inserted into the well, a cap 64 o is screwed onto the upper end of the casing to seal it.

done, since no supporting lines are required for the casing. I a V r Once the guide conduit and anchoring base are removed, the casing is supported from the vessel, and the casing cap and its line and valve are removed. Addi tional sections of casing are made up and the casing is lowered until the lower end of the casing is above the bottom of the well by a distance approximately equal to the water depth. An annular wellhead base 70 is j then'attached around the upper end of the casing, and a backoff joint 72,'made of two mating threaded pieces V 73, is welded to the casing above the wellhead base.

Additional sections of easing are then added to the backand is connected to a mud pit (not shown) from which drilling fluid is picked up by the pump and recirculated through the swivel and drilling equipment as described above. V

- Preferably, the casing is sealed in the well with cement 82 in a conventional fashion.

In the event the well is to be temporarily abandoned, say due to bad weather, the casing is rotated to uncouple the backoff joint 72 and is lifted and stored on the floating vessel. Before the casing is removed, a suitable guideline is temporarily anchored in the casing below the backoff joint and the upper end of the guide line is connected to a marker buoy. Thus, the buoy guides the floating vessel in returning to the well and the guideline is used in lowering the casing back down to make connection with the backoft'joint, so that drilling operations can be resumed as described above.

Thus, with the apparatus and methods of this invention, an underwater well can easily be started with a minimum of difliculty and equipment.

I claim:

1. The method for drilling a well in-an underwater formation from a floating vessel comprising the steps of anchoring the vessel over the underwater formation, disposing a guide conduit with its upper end terminating in the vicinity of the vessel and its lower 'end terminating in the vicinity of the formation, disposing drilling equipment in the guide conduit, operating the equipment to drill a well in the formation, withdrawing the drilling equipment from the well, lowering a casing through the guide conduit into the well, disposing theuppcr end of the casing to be in the vicinity of the floating Vessel,

' sealing the lower end of thecasing in the well, -stripping the guide conduit up off the upper end of the casing, disposing drilling equipment in the casing, and operating the equipment in the casing to drill the well deeper.

2. The method for drilling a well in'an underwater formation from a floating vessel comprising the steps of anchoring the vessel over the underwater formation, disposing a guide conduit with its upper end terminating in the vicinity of the vessel and its lower end terminating above the formation to leave a free space between the formation and the lower end of the conduit, disposing drilling equipment in the guide conduit, operating the 05 joint, and the icasing is lowered until the wellheadbase rests on the ocean floor and the upper end of the vcasing terminates just below the rotary table, as shown in FIGS. An annular buoyant chamber 74 is secured around the. upper portion of the casing below the water equipment to drill a well in the formation, withdrawing the drilling equipment from the well, lowering a casing through the guide conduit into the well, disposing the upper end of the casing to be in the vicinity of the floating vessel, sealing the lower end of the casing in the well, stripping the guide. conduit up off the upper end of the casing, disposing drilling equipment in the casing, and operating the equipment in the casing to drill the well deeper.

3. The method for drilling a well in an underwater formation from a floating vessel comprising the steps of anchoring the vessel over the underwater formation, disposing a guide conduit with its upper end terminating in the vicinity of the vessel and its lower endterminating in the vicinity of the formation, disposing drilling equipment in the guide conduit, operating the equipment to drill a well in the formation, withdrawing the drilling equipment from the well, lowering a casing through the guide conduit intothe well, disposing the upper end of the casing to be in the vicinity ,of the floating vessel, making the casing substantially buoyantgstripping the guide conduit up over the upper end of the'casing, sealing 'the lower end of the casing in the well, disposing drilling equipment in the casing, and operating the'equipmeht in the casing to drill the well deeper.

4. The method for drillinga Well in an underwater formation from ,a floating vessel comprising the steps of anchoring the vessel over the underwater formation, disposing a guide conduit withits upper end terminating in theivicinity of the vessel and itslower fend terminating in the vicinity of the formation, disposingdriilingequip ment in the guide conduit, operating the equipment to drill a well in the formation, withdrawing the drilling equipment from the well, lowering a casing through the guide conduit into the well, disposing the upper end of the casing to be in the vicinity of the floating vessel, making the casing substantially buoyant, stripping the guide conduit up over the upper end of the casing, thereafter adding additional sections of pipe to the upper end of the casing to increase its length, lowering the lengthened casing farther into the well, sealing the lower end of the casing in the well, disposing drilling equipment in the casing, and operating the equipment in the casing to drill the well deeper.

5. Apparatus for drilling a well in an underwater formation comprising a vessel floating in the water, a guide conduit depending from the vessel and terminating at its lower end in the vicinity of the underwater formation, means for anchoring the lower end of the guide conduit in fixed relation with respect to the formation, means for drilling a well in the formation through the guide conduit, means for removing the drilling means from the conduit, a casing capped at its upper end and adapted to be lowered into the well through the guide conduit, means for injecting and holding a fluid lighter than the water in the upper end of the casing when it is disposed in the guide conduit to make the casing substantially buoyant and means for lowering the casing into the well through the guide conduit and for raising the conduit up over the upper end of the casing when the casing is in the well.

6. Apparatus for drilling a well in an underwater formation comprising a vessel floating in the water, a guide conduit depending from the vessel and terminating at its lower end in the vicinity of the underwater formation, means for anchoring the lower end of the guide conduit in fixed relation with respect to the formation to leave an open space between the formation and the lower end of the conduit, means for drilling a well in the formation through the guide conduit, means for removing the drilling means from the conduit, a casing disposed in the guide conduit, means for making the casing substantially buoyant, and means for lowering the casing down through the conduit and into the well and for stripping the conduit up over the upper end of the casing.

7. Apparatus for drilling a well in an underwater formation comprising a vessel floating in the water, a guide conduit depending from the vessel and terminating at its lower end in the vicinity of the underwater formation, means for anchoring the lower end of the guide conduit in fixed relation with respect to the formation, means for drilling a well in the formation through the guide conduit, means for removing the drilling means from the conduit, a casing disposed in the guide conduit, means for making the casing substantially buoyant, and means for lowering the casing down through the conduit and into the well and for stripping the conduit up over the upper end of the casing.

8. The method for drilling a well in an underwater formation from a floating vessel and setting a casing into it, the method comprising the steps of anchoring the vessel over the underwater formation, disposing an elongated and upright guide conduit in the water with its upper end terminating in the vicinity of the vessel and its lower end terminating above the formation, securing the lower end of the conduit against lateral movement with respect to the formation and maintaining the interior of the lower end of the conduit open to the surrounding water, disposing drilling equipment in the guide conduit, operating the equipment to drill a well in the formation larger than the outside diameter of the casing, withdrawing the drilling equipment from the well, lowering a casing through the guide conduit into the well, sealing the lower end of the casing in the well, and stripping the guide conduit up off the upper end of the casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,263,661 Grant et al. Apr. 23, 1918 2,187,871 Voorhees Jan. 23, 1940 2,512,783 Tucker June 27, 1950 2,606,003 McNeill Aug. 3, 1952 2,777,669 Willis et al. Jan. 15, 1957 2,854,215 COX Sept. 30, 

